Is it or isn't it? False widow spider update

25 October 2013

Despite causing panic, the noble false widow will not cause you serious harm.

Recent reports in the press about spider bites have caused widespread alarm about autumn spiders, the vast majority of which are completely harmless. Our experts clear up some misconceptions.

Over the past few months, news reports about people having been bitten by false widow spiders have caused concern over the possible dangers of common spiders living in our homes and gardens.

No one has ever died of a spider bite in the UK. The Museum's Identification and Advisory Service (IAS) hears of about 10 cases of spider bites each year in the UK.

Not a spider invasion

Head of the Museum’s Angela Marmont Centre for UK Biodiversity Dr John Tweddle confirms that false widow spiders are becoming more common and more widespread as populations expand, but we shouldn't think of it as in influx.

The species associated with the bites, the noble false widow spider, has been living in the UK since the late nineteenth century, probably introduced here in ship cargo from the Canary Islands or Madeira.

We also tend to spot more spiders in the autumn because this is when the larger species reach maximum size, so are most visible. The males of some species also begin to move around more in search of a mate, so are more likely to be spotted.

The body length of an adult female false widow spider is around 15 millimetres, males are a little smaller. Maximum leg length of both sexes is about 25 millimetres.

Spider bites are extremely rare in the UK

False widow spiders, of which seven species have been recorded in the UK, are among only a dozen or so of the UK’s 650 species of spider that are capable of biting humans. But spider bites are extremely rare within the UK.

‘Even in homes with several resident false widow spiders you are statistically far more likely to be stung by a wasp or bitten by a dog,’ said Stuart Hine, Manager of the IAS.

The number of confirmed incidences of bites from false widow spiders remains low, although both adult males and females are certainly capable of biting humans if handled without due care.

The false widow not an aggressive species towards humans and is most likely to bite when accidentally prodded or squashed, or trapped in clothing.

‘In no way can this species be considered ‘deadly’ and to report so would be a gross exaggeration,’ said Hine. Media reports of severe symptoms are rarely backed up with identification of the spider that caused the bite, and may not be due to a spider at all.

‘In truth these extraordinary symptoms are more likely to be caused by other medical complications,’ said Hine, such as bacterial infection of a wound that may or may not be attributable to a spider bite.

‘I am happy living alongside this spider with my wife, three children, cat, dog and chickens,’ said Hine. ‘We are aware but not worried.’

Spiders are our friends

Spiders are natural enemies of many unwanted insect visitors. If you want to get rid of one from your house, it's best to catch and then release it away from your home.

Try to avoid touching them - as well as the small risk of bite, spiders are easily damaged. A cup and piece of card is a simple way to catch and then transport the spider out of your home.

Our identification forum, manned by Museum experts, has been flooded by enquiries and pictures asking for help. Hine has the following advice:

‘Be aware, learn how to distinguish this spider from other similar looking species and remove any from your home if you are inclined to.’

At this time of year, the missing sector orb weaver and the lace web spider are commonly mistaken for the false widow. The lace web spider may bite, but with little pain or lasting symptoms.

If you want to identify a spider in your home you can ask an expert in our NaturePlus identification forums.